Preparation of copolymers of dioxolanes and maleic anhydride

ABSTRACT

Copolymers are made by reacting maleic anhydride or a related compound with a 4-vinyl-1,3-dioxolane in the presence of a free radical initiator. The dioxolane reactant can be made by reacting a ketone with 3,4-epoxy-1-butene, or a substituted derivative thereof.

CROSS REFERENCE TO RELATED APPLICATION

This application is a division of application Ser. No. 498,178, filedMar. 23, 1990 now U.S. Pat. No. 5,019,635.

FIELD OF THE INVENTION

This invention relates to copolymers and to a method for theirformation. The copolymers are made by reacting maleic anhydride with a4-vinyl-1,3-dioxolane in the presence of a free radical initiator.

BACKGROUND OF THE INVENTION

Reaction of dioxolanes with a maleic anhydride has not been described inthe art. Hence, this invention provides new compositions and a methodfor their formation.

SUMMARY OF THE INVENTION

This invention relates to copolymers made from a 4-vinyl-1,3-dioxolaneand maleic anhydride or a substituted derivative thereof. The copolymersare alternating, i.e. they have a structure characterized by the formula--A--D--A--D--A--D--, wherein A is a monomeric unit derived from themaleic anhydride reactant, and D is a monomeric unit derived from a4-vinyl-1,3-dioxolane.

The 4-vinyl-1,3-dioxolanes used as reactants in this invention can beprepared by reacting a ketone with 3,4-epoxy-1-butene (EpB) or asubstituted derivative thereof. The dioxolane can be employed in thereaction mixture in which it is produced, or isolated and then used inthe process of this invention.

In the process of this invention, a maleic anhydride reactant is reactedwith a 4-vinyl-1,3-dioxolane in a solvent, or neat, and in the presenceof a free radical initiator. With regard to utility, the copolymerproducts of this invention are useful as chemical intermediates. Thereactive anhydride groups in the products can be used to crosslink thecopolymers with a variety of materials to produce useful coatings,films, binders, and dispersing agents for particulate materials. Theycan also be blended with other polymers to form coatings, films, pigmentbinders, etc.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In one embodiment, this invention comprises a copolymer having thealternating structure

    --A--D--A--D--A--D--                                       (I)

wherein A is a monomeric unit having the formula ##STR1## wherein each Ris independently selected from the class consisting of hydrogen,halogen, the cyano group, and primary and secondary alkyl groups havingup to about 4 carbon atoms, and D is a monomeric unit having the formula##STR2## wherein each R¹ taken independently is an alkyl or aryl grouphaving up to about 10 carbon atoms, or taken together are a divalentalkylene or arylene group having up to about 20 carbon atoms; each groupindicated by R² is hydrogen or an alkyl group having one to about fourcarbon atoms such that the total of the number of carbon atoms in saidR² groups, and the carbon atoms to which they are attached is up toabout 8.

In another embodiment, this invention provides a process for preparing acopolymer, said process comprising reacting a maleic anhydride reactanthaving the formula: ##STR3## wherein each R is independently selectedfrom the class consisting of hydrogen, halogen, the cyano group, andprimary and secondary alkyl groups having up to about 4 carbon atoms,and (B) a dioxolane having the formula ##STR4## wherein each R¹ takenindependently is an alkyl or aryl group having up to about 10 carbonatoms, or taken together are a divalent alkylene or arylene group havingup to about 20 carbon atoms; each group indicated by R² is hydrogen oran alkyl group having one to about four carbon atoms such that the totalof the number of carbon atoms in said R² groups, and the carbon atoms towhich they are attached is up to about 8 said process being conducted inthe presence of a free radical initiator.

As indicated above, this invention is related to copolymers and to amethod for their formation. The method for preparing the products ofthis invention comprises reacting a maleic anhydride reactant, e.g.maleic anhydride itself or an analog or homolog thereof, with adioxolane. The dioxolane can be prepared by reacting a butadienemonoepoxide with a ketone, using known methods e.g. F. G. Ponomarev,Proc. of the Acad. of Sciences of the USSR, Chem. Section, 108, 305(1956). Thus for example, the dioxolane can be made by reacting abutadiene monoepoxide reactant having the basic structure: ##STR5## witha ketone having the formula: ##STR6## In formulas IV and V above, theunsatisfied valences bind the carbon atoms from which they emanate toinert substituents, i.e. "inert groups". Such groups do not interferewith the formation of the dioxolane reactant. Furthermore, suchsubstituents do not interfere with the process of this invention bydecomposing to an undesired extent, under the reaction conditionsemployed to prepare the copolymer, or by undergoing one or moreextraneous side reactions when exposed to said reaction conditions, orby unduly hindering the process of this invention by steric hindrance,or by interfering with the formation of free radicals needed to initiateand/or conduct the process, or by some other hindering action.

Some preferred substituents that are suitable for use in this inventionhave already been disclosed above when describing R, R¹ and R².

When a ketone is used to prepare a 4-vinyl-1,3-dioxolane reactant usedin the process of this invention, it preferably has formula (VI).

In Formula (VI), each R¹ can be alike or different depending on whetherthe ketone is symmetrical or unsymmetrical. If the ketone is a cyclicketone such as cyclohexanone, the R¹ groups will not be separate groups.Instead, they together will be a 1,1-cyclo group, e.g.,1,1-cyclohexylidene. The R¹ groups are derived from ketones having up toabout 20 carbon atoms. Such compounds have the formula ##STR7## whereineach R¹ is alike or different. Preferably, R¹ is alkyl or aryl; morepreferably, primary or secondary alkyl. It is most preferred that eachR¹ be the same and selected from alkyl groups having up to about sixcarbon atoms. Straight chain alkyl groups of this type are highlypreferred. In other preferred compounds, R¹ can be halosubstitutedalkyl, more preferably perfluoromethyl. Preferred ketones are acetone,2-butanone, hexafluoroacetone, cyclohexanone and the like. The4-vinyl-1,3-dioxolanes can be prepared from such ketones by any methodapparent to one skilled in the art. For example they may be prepared byreacting an excess of the ketone with a butadiene monoepoxide having theformula ##STR8## wherein R² is as described above.

Although the process of this invention can be conducted using one ormore dioxolanes produced as previously described, it is to be understoodthat it is not necessary to do so. In other words, this invention is notlimited by the way in which the dioxolane (or the maleic anhydridereactant) is made.

In a preferred embodiment, dioxolanes employed in the process of thisinvention have up to about thirteen carbon atoms. Although more heavilysubstituted 4-vinyl-1,3-dioxolanes can be used in the process of thisinvention, those having up to about 13 carbon atoms are preferredbecause they, in general, are more readily obtainable.

Maleic anhydride can be used as a reactant in the process of thisinvention. Substituted maleic anhydrides can also be used. Whensubstituted, it is preferred that the maleic anhydride have up to about12 carbon atoms. However, reactants which have more than 12 carbon atomscan be used, as long as the substituents are "inert" as defined above.Highly preferred inert substituents (other than hydrogen) are methyl,chloro, and cyano. By way of illustration, analogues or derivatives ofmaleic anhydride having the formulas: ##STR9## can be used in thisinvention.

Because the polymers of this invention have an alternating structure asdescribed above, the monomers generally react in a mole ratio of 1 to 1.It is not necessary that the reactants be added to the reaction zone inthis ratio; an excess of either reactant can be employed. There is noreal upper limit on the amount of excess employed; this being defined bysuch secondary considerations as size of the reaction vessel, cost ofthe reactants, ease of separation of starting materials from products,etc. In general, one uses from about 0.5 to about 5.0 moles of onereactant per mole of the other. However, as discussed above it is to beunderstood that the composition of the polymer product is relativelyinsensitive to the ratio of reactants in the feed composition.

The process is conducted in the presence of a free radical initiator. Ingeneral, one employs a free radical initiator of the type known in theart such as azobisisobutyronitrile (AIBN), a benzoyl peroxide, hydrogenperoxide, butyl peroxide, and the like. The process can also beconducted in the presence of an amount of a redox initiator such asbenzoyl peroxide and N,N-diethylaniline which is sufficient to initiatethe reaction.

The amount of initiator employed is not critical. One employs enoughinitiator to achieve the desired result. Generally speaking, the amountof free radical initiator is from about 0.1 to about 10 weight percentbased on the amount of dioxolane. More or less initiator can be used, ifdesired. A skilled practitioner can readily determine whether an amountof free radical (or redox) initiator is adequate by adding the amount ofinitiator under investigation and determining by experimentation whetherinitiation occurs as desired.

The process of this invention is conducted in the presence of a solvent.It is preferred that the solvent boil at or above the initiationtemperature. Thus, when AIBN or a peroxide is used as an initiator, thesolvent preferably has a boiling point of about 40° C. or higher; morepreferably about 60° or above. When an ether is used as a solvent, onegenerally uses a monodentate, bidentate or tridentate ether having up toabout eight carbon atoms, and which has sufficient solvent power for thereactants and initiator, and which has a boiling point above theinitiation temperature. For the purpose of this invention, ethers havingone, two, or three ether linkages are designated respectively,monodentate, bidentate and tridentate ethers. Examples of such ethersare tetrahydrofuran, 1,4-dioxane, dimethoxyethane, diethyleneglycoldimethyl ether, and the like.

Ketones for use in this invention as solvent are preferably selectedfrom ketones which have sufficient solvent power for the reactants andinitiator, and also have a boiling point above the initiationtemperature. Examples of suitable ketones are cyclic and acyclic ketoneshaving three to about 20 carbon atoms such as acetone, 2-butanone,hexafluoroacetone, cyclohexanone and the like.

The concentration of reactants in the solvents is preferably in the15-95 weight percent range; however it is to be understood that reactantconcentrations somewhat outside this range can be used if desired. Apreferred concentration of monomers range is usually from about 25-50weight percent. It is to be recognized that a skilled practitioner maywish to operate outside the ranges given above. For example, an operatormay wish to use no solvent or a minimum amount of solvent in order toimprove process economics. Hence, the above ranges are not critical.

The process is started and conducted at convenient reaction temperatureswhich provide initiation of the reaction and a reasonable reaction rate.More than one temperature can be used. Thus, for example, the processcan be initiated at one temperature and conducted at anothertemperature, or at several temperatures. In general, when free radicalinitiation is employed, the process is initiated and conducted attemperatures between about -10° C. to about 180° C.

All of the materials used can be admixed prior to reaction.Alternatively, one may use a programmed addition of one or morematerials to the reaction mass.

The process proceeds well at ambient pressure. Thus, use of atmosphericpressure is preferred. However, subatmospheric and superatmosphericpressures can be used if desired. Superatmospheric pressures may bepreferably selected when a high temperature initiator is employed, orone or both of the reactants boil at a temperature below the selectedreaction temperature.

The reaction time is not a truly independent variable, but is dependentat least to some extent on the inherent reactivity of the reactants, thehalf life of the initiator, the reaction temperature employed, theconversion rate desired, etc. In general, process times in the range offrom about 1 to about 36 hours. Times within the range of from about 4to about 24 hours are preferred.

The molecular weight of the products of this invention is influencedsomewhat by the molecular weight of the starting monomers. Thus forexample the molecular weight of the product polymer will increase whenthe molecular weight of the monomers increase, unless the presence ofsubstituent groups on the monomer lowers the degree of polymerization insome manner. In general the number average molecular weight is in therange of from about 500 to about 20,000. Polymeric or oligomericproducts with a molecular weight range somewhat outside of this rangeare within the scope of the invention.

EXAMPLE 1

In a dry glove box under an inert atmosphere,2-ethyl-2-methyl-4-vinyl-1,3-dioxolane 1.42 g, 10 mmol; and maleicanhydride, 0.98 g, 10 mmol; were combined with 3.6 g of dry 2-butanonein a Claisen bottle having a magnetic stirrer, and then sealed. Theresultant mixture was heated at 70° C. with stirring for 20 hours.

The product solution was diluted with 5 g tetrahydrofuran (THF) andprecipitated into 200 ml heptane. The product was filtered, redissolvedin dry THF, and reprecipitated into ethyl ether, filtered, and dried toobtain a slightly yellow powder. The NMR spectrum was consistent with analternating polymer of maleic anhydride and the dioxolane. There were noremaining vinyl protons and the ethyl and methyl resonances from theenchained dioxolane were clearly discernible.

Yield=1.68 g (70% theory).

EXAMPLE 2

The procedure of Example 1 was followed, substituting 1.38 g of2,2-dimethyl-4-vinyl-1,3-dioxolane for2-ethyl-2-methyl-4-vinyl-1,3-dioxolane. NMR shows no vinyl protons andis consistent with a 1,2-propagation of the dioxolane monomer.

Yield=0.84 g, 36% theory. Size exclusion chromatography (SEC) in THF,Mn=1790, Mw=2800, Mn/Mw 1.56.

EXAMPLE 3

In a dry box under argon a Claisen bottle was filled with 0.71 g (5mmol) of 2-ethyl-2-methyl-4-vinyldioxolane, 0.49 g (5 mmol) maleicanhydride, 0.017 g AIBN (2% molar to dioxolane) and a magnetic stir bar.The reaction bottle was crimp-sealed, and placed in an oil bath at 70°C. with stirring for 24 hours. The reacted solid was dissolved with 10ml dry THF, and precipitated into rapidly stirred heptane. The solidpolymer (oligomer) was redissolved in dry THF, reprecipitated into ethylether (to remove any unreacted MAn) and collected using suctionfiltration. Yield was 1.13 g (94% theory). Mn=1340, Mw=2600, Mw/Mn=1.94.

EXAMPLE 4

A Claisen bottle was filled with 0.71 g (5 mmol) of2-ethyl-2-methyl-4-vinyldioxolane, 2.4 g toluene (33% by weightmonomers/solvent) 0.49 g (5 mmol) maleic anhydride, 0.017 g AIBN (2%molar to dioxolane) and a magnetic stir bar. The reaction bottle wascrimp-sealed, and placed in an oil bath at 70° C. with stirring for 24hours. Solid polymer precipitated out of solution and coated the wallsof the reaction bottle. The polymer solution was dissolved with 5 ml dryTHF, and precipitated into rapidly stirred heptane. The solid polymer(oligomer) was redissolved in dry THF, reprecipitated into ethyl ether(to remove any unreacted MAn) and collected using suction filtration.

Yield was 0.56 g (47% theory). Mn=1330, Mw=2240, Mw/Mn=1.68.

EXAMPLE 5

A reaction similar to that described in Example 4 was run substituting1,2-dichloroethane for toluene. The polymer remained in solution, wasdiluted with dry THF, and precipitated to obtain 0.60 g (50% theory) ofsolid polymer.

Proton NMR Spectra (in deuterated dioxane) of the polymers obtained fromExamples 3-5 were substantially the same.

The invention has been described in detail above with particularreference to preferred embodiments thereof. A skilled practitioner,familiar with the above detailed description can make many changes andsubstitutions without departing from the scope and spirit of theappended claims.

We claim:
 1. A process for preparing a copolymer having the formula--A--D--A--D--A--D-- wherein A is a maleic anhydride unit and D is adioxolane unit, said process comprising reacting (A) a maleic anhydridereactant having the formula: ##STR10## wherein each R is independentlyselected from the class consisting of hydrogen, halogen, the cyanogroup, and primary and secondary alkyl groups having up to about 4carbon atoms, and (D) a dioxolane having the formula ##STR11## whereineach R¹ taken independently is an alkyl or aryl group having up to about10 carbon atoms, or taken together are a divalent alkylene or arylenegroup having up to about 20 carbon atoms; each group indicated by R² ishydrogen or an alkyl group having one to about four carbon atoms suchthat the total of the number of carbon atoms in said R² groups, and thecarbon atoms to which they are attached is up to about 8, said processbeing conducted in the presence of a free radical initiator.
 2. Theprocess of claim 1 conducted at a temperature in the range of from about-10° to about 180° C.
 3. The process of claim 1 being conducted in thepresence of an inert organic solvent.
 4. The process of claim 3 whereinsaid solvent is selected from ethers and ketones.
 5. The process ofclaim 4 wherein said solvent is a ketone.
 6. The process of claim 5wherein the carbonyl group in said ketone solvent is bonded to the R¹groups present in said dioxolane.
 7. The process of claim 1 wherein saidmaleic anhydride reactant is maleic anhydride and said dioxolane is2-ethyl-2-methyl-4-vinyl-1,3-dioxolane.
 8. The process of claim 1wherein said maleic anhydride is reacted with2,2-dimethyl-4-vinyl-1,3-dioxolane.
 9. The process of claim 1 beingconducted in the absence of added solvent.